1. Field of the Invention
The invention relates to the operation of vehicles fueled by compressed natural gas (CNG).
2. Prior Art
Even though natural gas is in universal use as a household and commercial fuel, the acceptance of compressed natural gas as fuel for motor vehicles, in particular those for personal transportation, has been hampered by its low volumetric energy density as compared with that of the common liquid fuels, gasoline and diesel fuel. This manifests itself in lower power and performance, a more expensive and heavier fuel storage, shorter range, and a larger share of the useful vehicle space occupied by the fuel system as compared to vehicles fueled by liquids. The developments of the last 20 years have largely minimized these drawbacks such that vehicles powered by internal combustion engines designed for natural gas combustion approximate, in their overall performance, those powered by liquid fuels.
In the past there have been instances where in times of extreme scarcity of liquid fuels, local availability of natural gas made it the fuel of choice. An example is the Po valley of Italy in the years after the 2nd World War, 1947-9. There the majority of vehicular traffic was powered by the abundant, locally produced natural gas.
While presently there is no mass production of CNG vehicles, local availability of cheap natural gas results in some low level conversion of vehicles, primarily light trucks, to this fuel. At present the price of liquid hydrocarbons is low and their availability is high so that the market impetus for wider implementation of natural gas is absent. This condition can change in the future and the ample domestic resources of natural gas might be drawn upon for fueling personal transportation vehicles. Also, environmental constraints, both localized as in the Los Angeles Basin and global, as related to the climate change concerns, may promote the use of natural gas for vehicular transport since it presents a practical, large volume, alternative to gasoline and diesel fuel.
Any widespread use of vehicles using a gaseous fuel may lead to various alerting devices located on the vehicle itself as well as in parking garages. These are some of the problems this invention overcomes.